This invention relates to a method and an apparatus for pneumatically feeding fiber tufts to at least one fiber processing machine such as a carding machine, and is in particular concerned with the control and regulation of the flow rate of the air/fiber stream in the pneumatic duct leading toward the fiber processing machine. The pneumatic duct may deliver fiber tufts, for example, from a fine opener to a separate feed chute arranged upstream of each fiber processing machine. The conveying air stream is generated by a blower arranged in the fiber transporting duct.
In fiber tuft supplying systems, particularly those operating pneumatically, the operation may be adversely affected in case the air quantities emanating from the fiber supplying machines (such as the above-noted fine opener) and the fiber quantities admitted to the target machines (such as a fiber tuft feed chute for a carding machine) are not identical for an optimal operation. Thus, in a known arrangement drawbacks have been encountered in case the air streams or pressures fluctuate over time. In case the fiber transporting duct is not airtight, an air stream M.sub.3 may cape. The flow rate of an airstream M.sub.1 (which is present in the pneumatic duct from the pressure side of the blower to the escape location of the air stream M.sub.3), an air stream M.sub.2 (which is present from the escape location of the air stream M.sub.3 to the target machine) and the air stream M.sub.3 are coordinated for a determined operational point, for example, for a counterpressure p.sub.2. In case the pressure p.sub.2 changes, for example, because of a varying fill height in the feed chutes or because of a change in the number of consumer machines (such as carding machines), then in case of a throttling of the air stream M.sub.2, the flow rate of the air stream M.sub.3 increases unproportionately. This results in the disadvantage that a pressure build-up for p.sub.2 --which is technologically required for an optimal filling effect--cannot take place.